1. Field of the Invention
The present invention relates to a method of cleaning a dry-etching apparatus. In particular, it relates to a cleaning method for an etching apparatus for a semiconductor device, the method being provided to assure that the etching rate of a film to be etched, the in-plane uniformity of etching rate of the film to be etched and the etching rate ratio (selectivity rate) between the film to be etched and a mask material or an underlying material are less variable and reproducible and to keep a stable apparatus condition by minimizing emission of foreign matters in the apparatus.
2. Description of the Related Art
In manufacturing processes of semiconductor devices, etching techniques are used for forming fine patterns. The etching techniques are classified into the dry etching type and the wet etching type, and the dry etching technique has recently become mainstream due to its high workability. Known dry etching techniques include microwave plasma etching and reactive ion etching, both of which involve introducing an etching gas to a vacuum vessel and exciting the etching gas into a plasma using cyclotron resonance or high-frequency electric field, thereby etching a film to be etched.
On the other hand, as an element wiring material for semiconductor devices, aluminum (Al) is used. With the recent increase of the packaging density of semiconductor devices, the elements are becoming smaller and smaller, and materials that are more chemically stable and have lower resistances are attracting more attention. For example, gold (Au) is considered as an alternative to aluminum. Besides, a film of platinum (Pt), silver (Ag), titanium (Ti), titanium nitride (TiN), titanium oxide (TiO) or an aluminum alloy or a stack of films of these materials may be used. In addition, the device structure is becoming thinner, and the photoresist (PR), the oxide (SiO2) film, the titanium (Ti) film, and the titanium nitride (TiN) film serving as a mask, and the oxide (SiO2) film and an organic film serving as a base material are required to have a high selectivity.
In order to achieve a high selectivity, etching may be conducted using, as an etching gas, a mixed gas produced by adding at least one of methane (CH4), ethane (C2H6), acetylene (C2H2), dichloromethane (CH2Cl2), dibromomethane (CH2Br2), chloromethane (CH3Cl), bromomethane (CH3Br) and fluoromethane (CH3F) to at least one of chlorine (Cl2), boron trichloride (BCl3) and hydrogen bromide (HBr).
However, since a hydrocarbon (CH)-based gas is used as the additive gas, a hydrocarbon (CH)-based product is deposited in the apparatus during etching of the film to be etched. In addition, an etching residue of the film to be etched and a reaction product as a result of reaction of the film to be etched and the etching gas are not discharged and are deposited in the apparatus. Such deposite piles all cause reduction of etching performance and occurrence of a foreign matter and, therefore, have to be removed as required.
In order to remove the deposite pile in the vacuum vessel, dry cleaning that involves plasma processing or wet cleaning that involves opening the vessel to the atmosphere may be utilized. Typically, from the viewpoint of the productivity of the semiconductor device, the dry cleaning, which can be done in a shorter time, is selected. For example, known conventional dry cleaning techniques are as follows:
(1) a method of removing a carbon-based deposite pile (see Japanese Patent Publication No. 6-53193 or Japanese Patent Publication No. 9-36085, for example); and
(2) a method of removing a deposite pile of aluminum (Al), titanium nitride (TiN) or an aluminum alloy (see Japanese Patent Publication No. 2000-12515, for example).
The methods described above are to remove the deposite pile in the vacuum chamber by plasma processing using a selected cleaning gas. There has not been disclosed any method for removing a deposite pile formed when a film of gold (Au), platinum (Pt), silver (Ag), titanium (Ti), titanium nitride (TiN), titanium oxide (TiO), aluminum (Al) or an aluminum alloy or a stack of the films is etched using a mixed gas produced by adding at least one of methane (CH4), ethane (C2H6), acetylene (C2H2), dichloromethane (CH2Cl2), dibromomethane (CH2Br2), chloromethane (CH3Cl), bromomethane (CH3Br) and fluoromethane (CH3F) to at least one of chlorine (Cl2), boron trichloride (BCl3) and hydrogen bromide (HBr).